best m20 stroker combination.

[RobertC]

what mm pistons did you use? sport or ralley?

86mm Sport

[Chriskbmx]

nice. i was thinking about using the ralley for the slightly higher compression and better combustion characteristics.

[saurey]

Noob here. What's with those eBay kits? Like this one:

http://www.ebay.com/itm/BMW-325i-3-SERIES-1984-1991-E30-M3-M20-320-323-325-390HP-Turbo-Kit-3series-NEW-/271124396274?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f2045f8f2&vxp=mtr

Could I just give it to a good shop and say go to town and get results?

[F34R]

That is for a turbo kit, not even close to the same thing as a stroker build.

[tinkerputzer]

If I'm not mistaken, those headers have a 1 3/8 primary, this is NOT ideal in the extreme. 1 3/8 is only ideal on a pretty much stock engine, the reason behind that size is that packaging into the E30 chassis can be pretty tight. You'd be much better off with an 1.5" or maybe 1 5/8".

I agree. A stroker of this magnitude would be better suited with larger primaries. Although I'm running them and still making 210 whp and 218 wtq. The advantage to them is the quality you get for the price.

[Chriskbmx]

as far as exhaust im most interested on how the runner lenths change rpm ranges and such?

[Bullet Ride]

If I'm not mistaken, those headers have a 1 3/8 primary, this is NOT ideal in the extreme. 1 3/8 is only ideal on a pretty much stock engine, the reason behind that size is that packaging into the E30 chassis can be pretty tight. You'd be much better off with an 1.5" or maybe 1 5/8".

The OP said he wants a great power band with lots of torque. Based on what the OP wants I'd say that a header with long tubes and a smaller primary diameter would better suit his application. I see and hear people say from time to time that 1 3/8" is too small, but usually they don't provide any evidence to support that (i.e. a dyno plot of the same motor with 1 3/8" primaries vs 1 1/2" primaries).

Generally, primary size affects where peak torque will occur, and primary length affects how much of your torque is above or below your peak torque rpm. There are tools out there that give rough estimates of what your primary diameter should be based on where you'd like your peak torque to be. For example if you were to write the equation on this website (http://victorylibrary.com/mopar/header-tech-c.htm) for a 6-cyl motor you'd have:

OD = (RPM × Motor Size ÷ 415,633)^.5 + .098”

If you plug in 183ci (3L) into that equation you'll see that for a 3500rpm peak torque you'd want a 1.34" primary and that for a 4000rpm peak torque you'd want a 1.43" primary. A 1 1/2" primary would put your peak torque around 4464rpm. When I compare the result that this equation gives to my dyno result I do see a correlation



For a 2.8L (171ci) motor a peak torque at 4000rpm would require a 1.38" primary. I'm running the Bavauto headers which have 1.38" primaries and my peak torque was around 4000rpm. Obviously there are other variables at play such as cam profiles, cam timing, collector design, etc, but generally I haven't seen anything yet to prove that 1 3/8" primaries would be holding back an M20 stroker.

[SkiFree]

I agree with your methodology and theory, however the real world results aren't quite so concise. What I'm telling you is based from the results of a dyno-comparo did between long tube 1.5 vs 1 3/8 primaries (on a mildly modified M20). Yes, the 1 3/8" pipes didn't lose power, but they did not gain near as much as the 1.5's. And while its convenient to say, I simply don't have the slightest clue where that graph is anymore. Rather not argue on a message board.

I'm sure if the OP called MM where his pistons cam from, they'd tell him something similar.

[digger]

A S50 crank and bigger bore places significantly more demand on the head and if you use a 272 cam you aren’t increasing the flow capacity enough to compensate. I think you will be lucky to make 200whp with a 272 on a 3L it’s going to peak too low. It would have good midrange though.

[digger]

as for not needing a tuned set of headers i think that is not true ive never seen any M20 make respectable numbers without a good header it doesn't just bump up hp more so the midrange power (torque).

[digger]

this is a 1 5/8" header on a stock B25 still works pretty good though doesn't mean the same design in a 1 3/8" or 1 1/2" wouldbnt be be better

http://www.e30zone.net/e30zonewiki/images/6/62/Btb12.jpg

pipemax recommends 1 3/8" incase anyone was curious for a decent 2.7L

[ClassiE30]

Just did a nice stroker build for a customer.

2.7 Eta Crank
S50 135mm Rods
Metric Mechanic Pistons
Metric Mechanic Prepped cylinder head with Race/Rally Cam
Bav Auto style Headers
Stock Intake 19lb injectors
WAR Chip/MAF

With dyno tuning we pulled 197hp to the rear wheels.

Damn! Thats what Im looking for. Are you SoCal local?

Sent from my Note5

[CamE30]

If you are looking close to 200 you will need atleast a 2.8l or a 2.7 with ITBS.

Im running 524td crank, CP pistons, 86mm bore, 135mm Eagle H-BeamRods, BimmerHeads cam and racesprings and 19lb injectors with stock intake, stock AFM, no head porting and ebay headers.

[IMG][/IMG]

This a little before and after for kicks and giggles. This was a few days after the build was done. I had it re-dynoed at it makes closer to 198hp and 215ftlbs. You can see where the intake definitely limits the power in the upper RPMS.

[digger]

Time for RHD, ported head, MS pnp etc....

[CamE30]

Already in the works, cant wait to see how it will respond. The ITBS just showed up today.